A typical reciprocating saw is disclosed in GB 2 234 033. The reciprocating saw disclosed therein comprises a housing having a handle portion and a front portion from which a saw blade extends. The saw blade is guided for reciprocating movement and is connected to a drive mechanism within the housing which drives the saw blade to reciprocate. A typical example of saws of this kind are pruning saws used for cutting the branches of trees, bushes and the like. In this field of application the user holds the saw at the handle portion and brings the reciprocating saw blade into contact with the branch to be cut. The reciprocating saw blade is slowly moved through the branch while cutting it. The reciprocating movements of the saw blade exert forces on the object which is sawn, i.e. the object, for example a branch, tries to follow the reciprocating movement of the saw blade since there is a considerable friction between the reciprocating saw blade and the branch. Therefore, the user has to grip the branch and hold it tightly with one hand against the saw, while the pruning saw is held in the other hand in order to achieve an accurate cut. The need to hold the object, e.g. a branch, to be sawn with the reciprocating saw can make the saw very inconvenient to use.
Another problem or inconvenience arises due to the fact that the user has to absorb the oscillating forces which act between the reciprocating saw and the object which is sawn. When the user grips the branch to be cut and holds the reciprocating saw with the other hand he has to absorb the reciprocating forces acting between the branch and the saw with his arms. On the one hand this makes use of the saw tiring, and on the other hand, since the user cannot hold the branch completely fixed, the cut can be inaccurate if the saw is not steadily held in the same position with respect to the branch.
The problems outlined above do not apply to pruning saws only but to reciprocating saws in general. Whenever the object to be sawn has a certain flexibility or is not fixed and so has to be held by the user, for example when a rod has to be cut into pieces of shorter length, problems as described above arise.
The problems are further exacerbated when the branches of trees and bushes high above a user are cut using a reciprocating saw mounted on an extension arm or pole. In this case a user cannot reach the branch to be cut to hold it while it is cut. Thus, the reciprocating movement of the blade is transferred to the branch and the branch reciprocates also. This reduces the cutting performance of the saw, can lead to inaccurate cuts being made and tends to increase the length of time required to complete the task in hand.
It is therefore desirable to have a clamping device to hold the object to be saw stationary to prevent it from following the reciprocating movement of the saw blade whilst allowing the saw blade to cut through the object.
One such clamping device for a compass saw is disclosed in GB 2,182,282 and comprises a clamping holder in the form of a part circular bracket which is pivotally mounted at its centre on the body of the saw. On one arm of the part circular bracket is a clamping jaw having two inwardly facing clamping surfaces. On the other arm of the part circular bracket is a clamping part which comprises a threaded shaft which screws through a corresponding threaded hole, the direction of travel of the shaft as it screws into or out of the hole being within the plane of the clamping device either towards or away from the clamping jaw. In operation, the workpiece to be cut is inserted into the region bounded by the part circular bracket and is clamped between the clamping part and the clamping jaw by screwing the clamping part towards the clamping jaw and trapping the workpiece in between. As the blade of the saw cuts through the workpiece, the clamping device pivots to allow the workpiece to remain in contact with the cutting edge of the saw blade.
The clamping device disclosed in GB 2,182,282 must be firmly attached to the object to be sawn by the user prior to commencing the sawing operation. This can be difficult if the object to be sawn is located in an awkward position, for example, if it is a branch high up in a tree. The user is required to use both hands whilst attaching the clamp, one to hold the clamping device against the object to be cut whilst the other tightens the clamping part to hold the object to be cut. Furthermore, as the clamping device is firmly attached to the object to be cut, the only movement relative to the object to be cut which the body of the saw can make whilst cutting through the object to be cut is a pivotal movement. This may be undesirable in certain situations where there is insufficient room for the body of the saw to pivot.
DE 4429408 also disclosed a clamping device for a compass saw. The clamping device comprises a structure similar to a pipe wrench which is pivotally mounted on the saw housing. The object to be sawn is clamped by turning a knob which in turn rotates a threaded spindle to bring two clamping surfaces of the wrench into engagement with and thus hold the object. The clamping device disclosed in DE 4429408 suffers from the same problems as those suffered by the clamping device in GB 2,182,282.